Suda T, Zlotnik A
DNAX Research Institute of Molecular and Cellular Biology, Palo Alto, CA 94304.
J Immunol. 1992 Jul 1;149(1):71-6.
We previously reported that CD25 (IL-2R p55)-positive CD3-CD4-CD8- murine thymocytes can be induced to express CD8 alpha (Lyt-2) by transforming growth factor-beta plus TNF-alpha in the presence of IL-7 (which is necessary to maintain the viability and differentiation capacity of CD25+CD3-CD4-CD8- thymocytes in vitro). The majority of cells recovered after 2 to 3 days from these cultures expressed CD8 alpha (but not CD3 or CD4). In this study, we have characterized these in vitro generated CD3-CD4-CD8 alpha + thymocytes and compared them with normal CD3-CD4-CD8+ thymocytes. Unlike normal CD3-CD4-CD8+ thymocytes that express CD8 alpha and CD8 beta (Lyt-3-chain) simultaneously, only a fraction of in vitro generated CD3-CD4-CD8 alpha + cells expressed CD8 beta. However, along with the induction of CD8 alpha and CD8 beta expression, the expression of other T cell differentiation markers (including CD2, CD25, and CD44) also changed in a manner corresponding to physiologic differentiation. Cell-surface phenotyping suggests that CD8 alpha + beta - cells are less mature than CD8 alpha + beta + cells. These in vitro generated CD3-CD4-CD8 alpha + thymocytes expanded and differentiated into the CD4+CD8+ stage as well as mature (CD3+) single positive (CD4+CD8-) and CD4-CD8+) stages in fetal thymus organ culture that had been depleted of lymphoid cells by treatment with 2-deoxyguanosine. The latter observation indicates that these in vitro generated CD3-CD4-CD8 alpha + thymocytes are responsive to other differentiation-inducing signals (including those that induce CD4) that exist in fetal thymus organ culture. These results suggest that in vitro generated CD3-CD4-CD8 alpha + thymocytes represent intermediate differentiation stages between CD25+CD3-CD4-CD8- and CD3-CD4-CD8+ cells found in normal thymus.
我们之前报道过，在白细胞介素-7存在的情况下（白细胞介素-7对于在体外维持CD25⁺CD3⁻CD4⁻CD8⁻胸腺细胞的活力和分化能力是必需的），转化生长因子-β加肿瘤坏死因子-α可诱导CD25（白细胞介素-2受体p55）阳性的CD3⁻CD4⁻CD8⁻小鼠胸腺细胞表达CD8α（Lyt-2）。从这些培养物中培养2至3天后回收的大多数细胞表达CD8α（但不表达CD3或CD4）。在本研究中，我们对这些体外产生的CD3⁻CD4⁻CD8α⁺胸腺细胞进行了表征，并将它们与正常的CD3⁻CD4⁻CD8⁺胸腺细胞进行了比较。与正常的同时表达CD8α和CD8β（Lyt-3链）的CD3⁻CD4⁻CD8⁺胸腺细胞不同，体外产生的CD3⁻CD4⁻CD8α⁺细胞中只有一部分表达CD8β。然而，随着CD8α和CD8β表达的诱导，其他T细胞分化标志物（包括CD2、CD25和CD44）的表达也以与生理分化相对应的方式发生了变化。细胞表面表型分析表明，CD8α⁺β⁻细胞比CD8α⁺β⁺细胞成熟度更低。这些体外产生的CD3⁻CD4⁻CD8α⁺胸腺细胞在经2-脱氧鸟苷处理而耗尽淋巴细胞的胎胸腺器官培养物中扩增并分化为CD4⁺CD8⁺阶段以及成熟的（CD3⁺）单阳性（CD4⁺CD8⁻和CD4⁻CD8⁺）阶段。后一观察结果表明，这些体外产生的CD3⁻CD4⁻CD8α⁺胸腺细胞对胎胸腺器官培养物中存在的其他分化诱导信号（包括那些诱导CD4的信号）有反应。这些结果表明，体外产生的CD3⁻CD4⁻CD8α⁺胸腺细胞代表了正常胸腺中发现的CD25⁺CD3⁻CD4⁻CD8⁻和CD3⁻CD4⁻CD8⁺细胞之间的中间分化阶段。
